Martelli Saulo, Kersh Mariana E, Pandy Marcus G
Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, Bedford Park, Australia; North West Academic Centre, The University of Melbourne, St Albans, Australia.
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, IL, USA.
J Biomech. 2015 Oct 15;48(13):3606-15. doi: 10.1016/j.jbiomech.2015.08.001. Epub 2015 Aug 11.
The determination of femoral strain in post-menopausal women is important for studying bone fragility. Femoral strain can be calculated using a reference musculoskeletal model scaled to participant anatomies (referred to as scaled-generic) combined with finite-element models. However, anthropometric errors committed while scaling affect the calculation of femoral strains. We assessed the sensitivity of femoral strain calculations to scaled-generic anthropometric errors. We obtained CT images of the pelves and femora of 10 healthy post-menopausal women and collected gait data from each participant during six weight-bearing tasks. Scaled-generic musculoskeletal models were generated using skin-mounted marker distances. Image-based models were created by modifying the scaled-generic models using muscle and joint parameters obtained from the CT data. Scaled-generic and image-based muscle and hip joint forces were determined by optimisation. A finite-element model of each femur was generated from the CT images, and both image-based and scaled-generic principal strains were computed in 32 regions throughout the femur. The intra-participant regional RMS error increased from 380 με (R2=0.92, p<0.001) to 4064 με (R2=0.48, p<0.001), representing 5.2% and 55.6% of the tensile yield strain in bone, respectively. The peak strain difference increased from 2821 με in the proximal region to 34,166 με at the distal end of the femur. The inter-participant RMS error throughout the 32 femoral regions was 430 με (R2=0.95, p<0.001), representing 5.9% of bone tensile yield strain. We conclude that scaled-generic models can be used for determining cohort-based averages of femoral strain whereas image-based models are better suited for calculating participant-specific strains throughout the femur.
确定绝经后女性的股骨应变对于研究骨质脆弱性很重要。股骨应变可以通过结合有限元模型，使用按参与者解剖结构缩放的参考肌肉骨骼模型（称为缩放通用模型）来计算。然而，缩放过程中出现的人体测量误差会影响股骨应变的计算。我们评估了股骨应变计算对缩放通用人体测量误差的敏感性。我们获取了10名健康绝经后女性的骨盆和股骨的CT图像，并在六项负重任务期间收集了每位参与者的步态数据。使用皮肤安装标记距离生成缩放通用肌肉骨骼模型。通过使用从CT数据获得的肌肉和关节参数修改缩放通用模型来创建基于图像的模型。通过优化确定缩放通用和基于图像的肌肉及髋关节力。从CT图像生成每个股骨的有限元模型，并在整个股骨的32个区域中计算基于图像和缩放通用的主应变。参与者内部区域RMS误差从380 με（R2 = 0.92，p < 0.001）增加到4064 με（R2 = 0.48，p < 0.001），分别占骨拉伸屈服应变的5.2%和55.6%。峰值应变差异从近端区域的2821 με增加到股骨远端的34166 με。整个32个股骨区域的参与者间RMS误差为430 με（R2 = 0.95，p < 0.001），占骨拉伸屈服应变的5.9%。我们得出结论，缩放通用模型可用于确定基于队列的股骨应变平均值。而基于图像的模型更适合计算整个股骨的参与者特定应变。
